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Eastern New York Field Crops Pest Report, 2002

For 8/16/02:

Alfalfa

General: Established alfalfa stands were harvested this week, while new seedings are still 8-10 inches at SUNY Cobleskill (August 12).

Potato Leafhopper: Leafhopper infestations were below threshold in all alfalfa fields this week at SUNY Cobleskill (August 12).

Kathryn Evans (Madison County) reports a TAg alfalfa field over threshold for potato leafhopper (August 13).

Jonathan Wisbeski (Orange County) reports several alfalfa fields over threshold for potato leafhopper. He did state that potato leafhopper resistant alfalfa was far below threshold, (26 leafhopper/ 3 sets of ten sweeps / 18‰ alfalfa) while on the same farm a susceptible field was over the threshold (175 leafhopper/ 3 sets of ten sweeps / 15-18‰ alfalfa) (August 15).

Check out our on-line publication, Potato Leafhopper Management in Alfalfa

Field Corn

General: Conditions were still very dry at SUNY Cobleskill on Monday August 12. The no-till corn did not look as drought stressed as the conventional corn. We received a thunderstorm (.30 inch of rain) late in the day on Thursday, August 15 in Troy, NY. I am not sure how widespread the rain was in the area?

Corn Rootworm: At the SUNY Cobleskill farm, 3 of 6 fields were over threshold for corn rootworm this week. While scouting these fields I counted about 50% western corn rootworm and 50% northern corn rootworm (August 12).

Jeff Miller (Oneida County) reports several TAg cornfields over threshold for corn rootworm (August 16)

For more information on How to Monitor for Corn Rootworm check out our online publications:

Anthracnose Leaf Blight: Aaron Gabriel (Washington County) reports a cornfield with anthracnose leaf blight (August 6).

Anthracnose leaf blight appears as round to elongate, tan to brown water-soaked lesions, up to inch long and first appear on the lower leaves. Older lesions turn gray with small black specks in the center. Anthracnose inoculum survives on the corn residue left on the surface from the previous season. To control anthracnose leaf blight use resistant hybrids, rotate corn with non-grass crops or cleanly plow under infected residue.

Anthracnose stalk rot: How does European corn borer help anthracnose leaf blight infect corn?
Anthracnose stalk rot is the same fungus that causes anthracnose leaf blight. Stalk infection is more severe where there is injury by European corn borer. The holes bored by European corn borer in the stalks provide a means for the anthracnose fungus to enter the plant. Conditions that favor anthracnose stalk rot are continuous corn, surface corn residue (minimum & no tillage) and wet, humid, warm weather. Anthracnose stalk rot symptoms may appear after tasselling as vertical, tan to reddish brown, water-soaked lesions (streaks) in the rind. Lesions become large, dark brown to shiny black. To control anthracnose use resistant hybrids, rotate corn with non-grass crops or cleanly plow under infected residue. Fields with high amounts of anthracnose leaf blight should be checked for indications of anthracnose stalk rot. If stalk rot is found you may wish to target that field for early harvest to avoid losses associated with premature lodging.

Keep cool and happy scouting!